Hi In the files I sent you, is a spreadsheet for a shorter term trade (for ZNO) from memory which shows one way to set a stop loss using moving averages.
You may be able to adapt it for the vaguaries of day trading (with much lower averages) or you may consider wathcing the the book build and seeing where major levels of support and resistance are.
It is a matter of what suits your time in front of each trade.